By early 1942, as the United States suffered a series of military
defeats in the Pacific, top officials in Washington tentatively had
decided to proceed with the construction of an atomic bomb. Two
paths seemed possible. A
uranium bomb could be achieved if
sufficient uranium-235 could be produced by one or more of the three
isotope separation methods under consideration: gaseous diffusion,
centrifuge, and electromagnetic. A plutonium
bomb might provide a quicker route, but it required demonstration
that plutonium could be produced in a uranium pile and then be separated
in usable quantities. To this end, Arthur Compton consolidated most
plutonium research at the new Metallurgical Laboratory (Met Lab) at the
University of Chicago.

A program review conducted in May 1942 determined that no front runner
in the race for the bomb existed and recommended that the three isotope
separation methods and the pile project be pushed as fast as possible to
full production planning. Construction and security needs suggested
placing the program in the Army Corps of
Engineers. In
August, the Corps set up the Manhattan Engineer District (MED)
to manage the project. A month later, Colonel Leslie R. Groves was
promoted to brigadier general and appointed to head the effort.
Groves moved quickly to narrow the field
and move the project along, selecting a site in east Tennessee
(Oak Ridge) for the construction of production plants, dropping the centrifuge process from
consideration, and choosing J. Robert Oppenheimer to head the bomb research
and design laboratory to be built at Los Alamos, New Mexico. In December, President Franklin Roosevelt gave his final
authorization to proceed with construction of the atomic bomb.

To learn more about any of these difficult choices that had to be made in
1942, choose a web page from the menu below. To continue with a quick overview of the Manhattan Project, jump ahead to the
description of the "Uranium Path to the
Bomb, 1942-1944."